基于频域的液货船疲劳强度评估的理论与方法研究

Sloshing in liquid carries is one of the classical questions in hydrodynamics field, and is always concerned in academia and engineering field. Violent fluid motion happens when ship motion period is close to fluid natural oscillation period, although the external incentive is slight. Sloshing will result in serious questions, such as losing of ship stability, structural failure of the liquid cargo tanks, decrease of ship maneuverability, destruction of natural environment and ecological environment, great casualties and enormous property loss and so on. Therefore, theory and method research on fatigue evaluation of liquid tank thinking about sloshing is of important theoretical significance and great engineering practical value..In the project, based on frequency domain analysis, the theory and method research on fatigue evaluation about liquid tank thinking about sloshing will be accomplished through ship model experiment, numerical simulation, theoretical derivation and method promoting. The research content consists of five aspects. Firstly, sloshing mechanism research of the liquid will be carried out, in which, the relevant factors connected with the liquid sloshing will be discussed.Secondly, ship hydrodynamic performance will be completed, in which, the coupling effect of liquid sloshing and wave load will be analyzed. Thirdly, frequency domain analysis on sloshing load will be achieved, in which, the frequency relativity between sloshing motion and the wave load is put forward. Fourthly, spectral method is advanced,in which, the sloshing load and wave load are included. Fifthly, reliability analysis on the new method will be carried out,in which, the influence from time domain feature of sloshing load to assessment result is studied, and the comparison analysis whether think about the influence of sloshing is finished.

液货船舱内流体晃荡是水动力学经典问题，倍受学术界和工程界的关注。船体在波浪中的运动频率与液货振动固有频率相近时，很小的外部激励也可能引发剧烈的液体晃荡。液货晃荡将带来严重危害：导致船舶稳性的损失；造成结构失效破坏；影响舵的操作性；破坏自然环境和生态环境；造成重大人员伤亡和巨额经济损失。因此考虑液货晃荡的液货船疲劳强度评估的理论方法具有重要的研究意义。.项目通过模型试验、数值模拟、理论推导、方法提升，提出一种基于频域分析的考虑液货晃荡的船舶疲劳强度评估方法。研究内容包括：液货晃荡机理，研究影响液货晃荡的相关因素；液货船水动力性能研究，研究液货晃荡与波浪载荷的耦合作用；晃荡载荷的频域分析，研究晃荡与波浪的频率相关性；液货船疲劳强度评估的谱分析方法研究，考虑晃荡载荷和波浪载荷的共同作用；方法可靠性分析，研究晃荡载荷的时域特征对疲劳评估结果的影响，并进行考虑与不考虑晃荡的船舶疲劳损伤对比研究。

液货船舱内流体晃荡是水动力学经典问题，倍受学术界和工程界的关注。船体在波浪中的运动频率与液货振动固有频率相近时，很小的外部激励也可能引发剧烈的液体晃荡。液货 晃荡将带来严重危害：导致船舶稳性的损失；造成结构失效破坏；影响舵的操作性；破坏自然环境和生态环境；造成重大人员伤亡和巨额经济损失。因此考虑液货晃荡的液货船疲劳强度评估的理论方法具有重要的研究意义。 .项目通过模型试验、数值模拟、理论推导、方法提升，提出一种基于频域分析的考虑液货晃荡的船舶疲劳强度评估方法。研究内容包括以下四方面。.（1）液货船舱段的运动响应模型试验。包括模型试验方案设计、舱段缩尺比模型制作、规则波参数研究、舱段模型的运动控制装置研制、舱段运动数据采集装置研制以及考虑液货晃荡影响的舱段模型试验开展。.（2）考虑液货晃荡影响的液货船水动力性能研究。包括不同载液率、不同浪向角和不同纵舱壁形式下是否考虑液舱晃荡载荷的液货船运动模拟、有无晃荡载荷的液货船运动响应的对比研究以及不同装载率下液货船运动响应的对比研究。.（3）考虑晃荡影响液货船的结构整体强度评估研究。对11000DWT液货船开展了波浪诱导载荷的长期预报，并采用设计波法研究了液舱晃荡载荷对液舱结构响应的影响规律，对比研究了有无晃荡载荷的整船结构应力分布规律。.（4）考虑晃荡影响液货船的结构疲劳强度评估研究。采用谱分析法对11000DWT液货船船中货舱典型节点进行疲劳损伤预报，研究了液舱晃荡载荷对液舱结构疲劳强度的影响规律，对比研究了无晃荡载荷的船舶结构疲劳性能。